Background: Adherence has been defined as the extent to which a person's behavior is consistent with health care recommendations (Haynes, 1979). A number of different types of treatment adherence problems have been identified (Hoagland et al., 1983). These problems include: 1) failure to return following initial evaluation for recommended outpatient treatment; 2) failure to keep subsequent appointments; 3) patient refusal of the recommended inpatient and outpatient treatments; and 4) non-adherence with prescribed home medication regimens (Itano, Tanabe, & Lum, 1983). The problem of poor adherence is significant within health care and a concern across the whole continuum of care from prevention, through screening, treatment, and rehabilitation. The costs of dealing with the consequences of poor adherence to medication alone have been estimated to be in excess of $100 billion yearly (Dunbar-Jacob & Mortimer-Stephens, 2001). Although poor adherence has long been recognized as an important problem in medicine, relatively few studies have examined the seriousness of this problem in cancer (Peterman & Celia, 1998). Patients who fail to receive a full course of prescribed cancer therapy have been shown to be at increased risk of recurrence and potentially poorer survival outcomes (Richardson et al., 1990). For example, McCready et al. (2000) found that the rate of recurrence among postmenopausal women who underwent lumpectomy without adjuvant therapy was 24%, compared to those compliant with adjuvant therapy. Similarly, de Csepel et al. (2000) also found a higher lifetime rate of recurrence (22%) among elderly women treated with breast conservation surgery without adjuvant therapy who did not fully adhere to recommendations for radiation therapy following breast cancer surgery. As the number of cancer survivors grows it is becoming of increasing importance to do research to test whether or not adherence to adjuvant therapies or to recommended changes in health behaviors affects the risks of cancer recurrence.